The invention relates to a gas producer for filling a gas cushion restraining device for occupants of vehicles, having a combustion chamber filled with fuel and surrounded by a wall which exhibits apertures for the discharge of the gas produced, said apertures being sealed hermetically by a destructible cover at the start of the burning process of the fuel up to a specific pressure rise in the combustion chamber.
The efficiency of such gas producers is dependent on temperature, so that the gas cushion is inflated more rapidly at high temperatures of the fuel than at low temperatures. The reason for this is the dependence of the burning behaviour of the fuel upon temperature for a constant cross-sectional area of the nozzle of the combustion chamber. However, the strengths of the entire system, comprising producer, gas cushion, retaining means and, for example, steering wheel have to be dimensioned for the maximum efficiency of the producer at high ambient temperatures for safety reasons.
This dependence of the burning behaviour of the producer upon the temperature is also disadvantageous in another respect. Only a certain time, of 30 msec for example, is available for the filling of the gas cushion. This time is also required in full by a producer, the temperature of which is -30.degree. C. for example at the time of tripping or detonation. However, if the producer temperature at the time of the accident is +80.degree. C. for example, then the gas cushion will have been filled after only 24 msec, for example, which results in an unnecessary increase in the acoustic pressure with its negative effects upon the vehicle occupants.
It is therefore an object of the present invention to avoid these described disadvantages and to develop a gas producer so that a more uniform pressure curve is obtained irrespective of the inherent temperature of the producer at the time of tripping.
This object is achieved according to the invention in a generic gas producer, in that the total cross-sectional area of the discharge apertures is automatically enlargeable as a function of the rising combustion chamber pressure.